A new 'State of the World's Rivers' database shows how the world's rivers have been impoverished by dams and their ecosystems devastated - and provides a valuable resource to help save river basins that remain in good health.

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International Rivers has launched 'The State of the World's Rivers', an interactive online database that illustrates the role that dams have played in impoverishing the health of the world's river basins.

The database shows how river fragmentation due to decades of dam-building is highly correlated with poor water quality and low biodiversity. Many of the world's great river basins have been dammed to the point of serious decline, including the Mississippi, Yangtze, ParanÃ¡ and Danube. "The evidence we've compiled of planetary-scale impacts from river change is strong enough to warrant a major international focus on understanding the thresholds for 'river change' in the world's major basins, and for the planet as a whole system", said Jason Rainey, Executive Director of International Rivers.

For example, in the Middle East, decades of dam building in the Tigris-Euphrates basin have made it one of the most fragmented basins in the world.

As a result, the basin's flooded grassland marshes have significantly decreased, leading to the disappearance of salt-tolerant vegetation that helped protect coastal areas, and a reduction in the plankton-rich waters that fertilize surrounding soils.

Habitat has decreased for 52 native fish species, migratory bird species, and mammals such as the water buffalo, antelopes and gazelles, and the jerboa.

Largely intact river basins now at risk

Meanwhile, some of the lesser-dammed basins, which are still relatively healthy at this point, are being targeted for major damming.

For example, the most biodiverse basin in the world, the Amazon, still provides habitat for roughly 14,000 species of mammals, 2,200 fish species, 1,500 bird species, and more than 1,000 amphibian species, like the Amazon River Dolphin, the Amazonian Manatee, and the Giant Otter.

When all dam sizes are counted, Brazil plans to build an astonishing 412 dams in the ParanÃ¡ and 254 in the Amazon basins. In Asia, China plans to continue to dam the Yangtze basin with at least another 94 planned large dams. At least 153 more dams are planned for the Mekong basin.

Other basins that are high in biodiversity and water quality which are also targets for dam-building include the Tocantins, the Irrawaddy, the Congo, and the Zambezi.